"If seeds in the black earth can turn into such beautiful roses, what might not the heart of man become in its long journey towards the stars?"

From Maisie Ward's book "Return to Chesterton" [p. 161 in my edition]. The context of this scene being World War 1.
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...Then came August 4th and the beginning of another kind of tragedy. As the weeks dragged on the strain became greater and greater, but there had come also a lifting of the heart in Gilbert that responded to the heroism around him. Mrs. Meredith remembers keenly a November afternoon in the little study at Overroads. Gilbert was dictating and a newsboy was crying bad news underneath the window and announcing the death and the wounds of many young Englishmen. Gilbert paused in the detective story he was writing and after the pause he went on in a new voice:

"If seeds in the black earth can turn into such beautiful roses, what might not the heart of man become in its long journey towards the stars?"

As he spoke the boy's voice could still be heard, growing fainter as he vanished into the mist.